1. Technical Field
The present invention relates to a liquid developer and an image forming apparatus.
2. Related Art
As a developer to be used for developing an electrostatic latent image formed on a latent image carrying member, a liquid developer obtained by dispersing a toner made of a material containing a colorant such as a pigment and a binder resin in an electrically insulating carrier liquid (insulating liquid) is known.
In toner particles constituting such a liquid developer, a resin material such as a polyester resin, a styrene-acrylic ester copolymer or an epoxy resin has been used. Such a resin material has characteristics that it is easy to handle, a color developing property of the resulting image is good and a high fixing property can be obtained.
However, in a past liquid developer, a resin material constituting the toner particles and an insulating liquid had a low affinity for each other, and it was difficult to make the dispersibility of the toner particles in the insulating liquid sufficiently high.
In order to improve the dispersibility of such toner particles, an attempt to use a rosin resin with a high affinity for an insulating liquid as the resin material constituting the toner particles has been made (see, for example, Japanese Patent No. 3332961).
However, in the liquid developer described in Japanese Patent No. 3332961, although the initial dispersibility of the toner particles was good, the toner particles aggregated over time and it was difficult to maintain the dispersibility for a long period of time. Further, in the past liquid developer, sufficient chargeability could not be obtained, and in particular it was difficult to obtain positive chargeability.